At least back to 2018, NASA and the Department of Energy's National Nuclear Security Administration (NNSA) have been working on a portable nuclear reactor to power deep-space exploration, such as human missions to Mars in the next decade and beyond.

"Small nuclear reactors can provide the power capability necessary for space exploration missions of interest to the Federal government," the Energy Department wrote Friday.

The Dept. of Energy call for partners reads as follows: 

Battelle Energy Alliance, LLC (BEA), the managing and operating contractor for the U.S. Department of Energy's Idaho National Laboratory (INL), is seeking information from leaders in the nuclear and space industries to develop innovative technologies for a fission surface power (FSP) system that can be operated on the moon. The request for information can be viewed here. Responses are sought by Sept. 8. After receiving responses, INL will issue a request for proposal.

According to Time Magazine commentary, the plan includes two phases, described as first, "Developing a reactor design" and second: "building a test reactor, a second reactor be sent to the moon, and developing a flight system and lander that can transport the reactor to the moon."

"The goal is to have a reactor, flight system and lander ready to go by the end of 2026," the report says.